1. Field of Use
This invention relates generally to control lever assemblies for valve-operated hydraulic power shift transmissions and modulating master clutches such as are used in the power train on crawler tractors or the like. In particular, it relates to control lever assemblies having a manually operable gear selector lever for operating both the shift control valve for the transmission and the clutch control valve, and a manually operable safety lever for preventing engine-starting unless the transmission is in neutral.
2. Description of the Prior Art
In some control lever assemblies of the aforesaid character, the gear selector lever is movable laterally in opposite directions from a centered neutral position to forward or reverse speed range positions and is further movable fore and aft in each speed range position between slow and fast positions. The gear selector lever is connected to operate the shift selector valve for the transmission when moved laterally and is further connected to operate the modulating clutch control valve for the modulating clutch when moved fore and aft. The safety lever, which is movable fore and aft between an engine-start position to an engine-run position, is connected to operate an electric switch which must be actuated by placement of the safety lever in engine-start position before the engine can be started. The gear selector lever and safety lever are interlocked or interconnected so that the safety lever cannot be placed in engine-start position unless the gear selector lever (and transmission) is in neutral. Some prior art control lever assemblies of this type employed a very complex arrangement of linkages and bellcranks and were relatively difficult and costly to manufacture, install, adjust and service. Furthermore, speed variation in the speed range selected was rather limited and not always directly related to tractor speed and power requirements in particular situations.